The amount of supply air required in a ventilation system should be approximately equal to which of the following?

The proper functioning of a ventilation system relies on a balance between supply air, return air, exhaust air, and fresh air supply. In an ideal system, the amount of supply air introduced should match the sum of the return and exhaust air, ensuring that the indoor environment maintains air quality and proper pressure levels.

Supply air is the conditioned air delivered into a space. Return air is the air that is drawn back into the HVAC system to be reconditioned, and exhaust air is the air expelled from the space, often containing contaminants or excess humidity. Fresh air supply refers specifically to air that is introduced into the system from the outside to ensure adequate ventilation and improve air quality.

By maintaining this balance, the system can effectively remove stale air and replace it with fresh air, preventing issues of indoor air pollution and maintaining comfort levels. This requirement is reflected in many HVAC design principles and codes, including the International Mechanical Code, which ensures that the system operates efficiently and safely.

Selecting the option that includes all three aspects—return air, exhaust air, and fresh air supply—recognizes the interconnected nature of these components in a balanced ventilation system.